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MO: Fachverband Molekülphysik
MO 6: Femtosecond Spectroscopy 1
MO 6.1: Hauptvortrag
Dienstag, 18. März 2014, 10:30–11:00, BEBEL HS213
Time-resolved absorption studies of photoinitiator molecules in solution — •Andreas-Neil Unterreiner1, Hanna A. Ernst1, Thomas J. A. Wolf1, Dominik Voll2, Elena Frick2, and Christopher Barner-Kowollik2 — 1Institute of Physical Chemistry, Karlsruhe Institute of Technology (KIT), 76128 Karlsruhe, Germany — 2Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology (KIT), 76128 Karlsruhe, Germany
Understanding early-time dynamics of photo-induced polymerization can be important for successful high-tech applications. This also implies the development of search criteria for molecules showing e.g. efficient triplet radical initiation processes. In this context, it is important to accurately determine the efficiency for both radical formation after photo-excitation and polymerization of formed radicals. In this contribution, focus is given on the elucidation of the first steps particularly with regard to radical formation by reporting new results of type-I (radical formation after α-cleavage) photoinitiators. It will be shown that ultrafast intersystem crossing (ISC) on a picosecond timescale is one crucial process towards adequately describing polymerization efficiency although the relevant timescales (ISC and radical polymerization) differ by many orders of magnitude. In combination with time-dependent density functional theory (TD-DFT) calculations and pulsed laser polymerization with subsequent electrospray ionization mass spectrometry (PLP-ESI-MS) for post-mortem analysis of the polymerization products, one can obtain a more detailed picture of the relevant pathways of some recently published photoinitiator molecules.